Various fluid systems are employed in the drilling and maintenance of oil and gas wells. Such fluid systems include freshwater systems, saltwater systems, fresh-water-polymer systems, and saltwater-polymer systems. Undesirable foaming can occur in any of these systems.
Excessive foaming is a major problem when using polymers in fresh water and, particularly, in brine systems. Polymers and salts tend to promote bubble formation, even during a very modest circulation of fluid. Foam is formed as a result of a gas trying to break through the "skin" of surface tension of a liquid. When the surface tension is high, such high surface tension being caused by a strong inelastic "skin", the rising gas exerts sufficient strain to rupture this barrier. On the other hand, when the surface tension is low, such low surface tension being caused by polymers, salts, or treatment chemicals that are present in the environment, the rising gases will stretch the elastic "skin" into bubbles, consequently generating foam.
Various surface active agents or spreading agents have been employed to minimize or to prevent the formation of foam in a variety of fluid systems. For example, Finigan, et al., in U.S. Pat. No. 2,884,474, teach the use inter alia of non-ionic antifoam agents, such as sorbitan oleate and sorbitan trioleate, for desorption of butadiene-1,3 from an ammoniacal copper ion solvent. In U.S. Pat. No. 3,076,768, Boylan discloses the use of sorbitan trioleate, sorbitan monostearate, and polyoxyethylene sorbitan tristearate as defoamers in an inexpensive defoaming composition comprising a water-insoluble, organic liquid, such as kerosene and mineral oils, and a finely-divided hydrophobic silica suspended in the organic liquid. In U.S. Pat. No. 3,705,859, Boylan teaches that sorbitan monooleate can be added to an aqueous system to abate the formation of foam. In U.S. Pat. No. 4,105,802, Cho, et al., disclose the use of sorbitan monooleate as an antifoaming agent when producing a carbonated coffee drink. In U.S. Pat. Nos. 4,116,706 and 4,209,336, Previte discloses the use of synthetic non-ionic polyol surfactants, such as those sold commercially under the trade name "Pluronic", and non-ionic fatty acid partial esters of sorbitol anhydride, such as sorbitan monooleate, as surface active agents that are suitable for use in hydraulic cement compositions to enhance the compressive strength thereof. In U.S. Pat. No. 3,248,289, Shinozaki, et al., disclose a composition for the prevention and treatment of frothy bloat in ruminants, which composition can comprise as main active ingredients block polymers of two kinds of the same or different polyalkylene glycols, ethers of said polyalkylene glycols with primary alcohols, esters of said polyalkylene glycols with fatty acids, or fatty acids esters of anhydrosorbitol, such as sorbitan monooleate, and as adjuvants alcohols, such as octyl alcohol, octanol-2,2-ethylhexylalcohol, cyclohexanol, lauryl alcohol, cetyl alcohol, and stearyl alcohol, and higher glycols, and oils, such as soybean oil and castor oil.
Now there has been formulated a novel, biodegradable defoamer and antifoamer composition for use in any fresh-water system, saltwater system, freshwater-polymer system, or saltwater-polymer system. The resulting formulation not only causes surface bubbles to break on initial addition of the composition, but such composition continues to provide a protective barrier (antifoam) against additional foam caused by subsequent agitation of the fluid system.